Code Explanation:
🔹 1. Importing MappingProxyType
from types import MappingProxyType
✅ Explanation
MappingProxyType is imported from Python's built-in types module.
It creates a read-only view of a dictionary.
A read-only view means:
✅ You can read data.
❌ You cannot modify data through the view.
Think of it like a glass window.
Original Dictionary
│
▼
MappingProxyType
│
▼
Read Only View
Nothing is created yet.
🔹 2. Creating a Dictionary
data = {"x": 1}
✅ Explanation
A dictionary named data is created.
Current Memory
data
↓
{
"x": 1
}
Visual Representation
Key Value
x → 1
🔹 3. Creating a Read-Only View
view = MappingProxyType(data)
✅ Explanation
Python creates a read-only view of data.
⚠️ Important:
view does not create a copy.
It simply points to the same dictionary.
Memory Diagram
Dictionary
{"x":1}
▲ ▲
│ │
data view
Both variables refer to the same dictionary.
The difference is:
data → Read and Write
view → Read Only
🔹 4. Understanding the Shared Memory
Current Situation
data
↓
{"x":1}
▲
│
view
✅ Explanation
Since both point to the same dictionary,
if data changes,
view automatically sees the changes.
No duplicate dictionary is created.
🔹 5. Adding a New Key
data["y"] = 2
✅ Explanation
A new key-value pair is added to the original dictionary.
Before
{
"x":1
}
After
{
"x":1,
"y":2
}
Since view shares the same dictionary,
it immediately sees this new key.
Current Memory
data
↓
{
"x":1,
"y":2
}
▲
│
view
🔹 6. Accessing the Value Through view
view["y"]
✅ Explanation
Python searches for key "y" inside the shared dictionary.
Dictionary
"x" → 1
"y" → 2
Returned value
2
Notice that view can access the new key even though it was added after the view was created.
🔹 7. Printing the Value
print(view["y"])
✅ Explanation
Python prints the value associated with "y".
Output
2
🎯 Final Output
2
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